phpBB & Cookies

Hast du es denn schon über mehrere Browser versucht?, Welche Version des Browser nutzt du?

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Unabhängig davon, einen Ausschnitt der FAQ von phpBB 3.0 :

I (or my users) cannot stay logged in to the forum!

If you (or your users) are, after attempting a login, being returned to the index (or other page) without appearing to be logged in the most likely problem is incorrect cookie settings. phpBB uses cookies to store a session id and a small amount of user data. For this data to be stored correctly the cookie domain, name, path and secure settings must be correct. You can check this in Admin->General->Server Configuration->Cookie Settings. Typically the cookie domain can be left blank and the cookie path set to / (a single forward slash). Do not set the cookie as being secure unless your board is running over a secure sockets layer connection, ie. https://

If you still have problems try setting the cookie domain to your full domain name, eg. http://www.mysystem.tld, http://www.something.mydomain.tld. You must ensure the domain name contains at least two dots or browsers will be unlikely to recognise the cookie, eg. .mydomain.com, mydomain.com. Do not add http:// or anything else to the domain name!